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Abstract:

Cement compositions and methods for making cement compositions are
provided. The cement compositions can comprise at least one oxide having
a particle size of less than about 600 nm. The methods for making cement
may include: providing a mixture of compounds containing the required
calcium, silicon, aluminum, and iron to provide at least one of
tricalcium silicate, dicalcium silicate, tricalcium aluminate,
tetracalcium aluminoferrite, other calcium silicates, aluminates,
ferrites, and silicates or combinations thereof; adding a fuel source and
an oxidizer to the mixture of compounds; and heating the mixture of
compounds, the fuel source, and the oxidizer such that the mixture of
compounds, the fuel source, and the oxidizer ignite to form the at least
one tricalcium silicate, dicalcium silicate, tricalcium aluminate, and
tetracalcium aluminoferrite, or combinations thereof,

Claims:

1. A cement composition, comprising at least one oxide having a particle
size of less than about 600 nm, wherein:the at least one oxide is
selected from tricalcium silicate, dicalcium silicate, tricalcium
aluminate, and tetracalcium aluminoferrite, other calcium silicates,
aluminates, ferrites, silicates or combinations thereof; andthe at least
one oxide is made by:providing a mixture of compounds containing the
required calcium, silicon, aluminum, and iron for the at least one
oxide;providing a fuel source and an oxidizer to the mixture of
compounds; andheating the mixture of compounds, the fuel source, and the
oxidizer such that the mixture of compounds, the fuel source, and the
oxidizer ignite to form the at least one oxide.

2. The composition as claimed in claim 1 wherein the step of heating
comprises heating the mixture of compounds, the fuel source, and the
oxidizer such that the mixture of compounds, the fuel source, and the
oxidizer all foam and subsequently ignite to form the at least one oxide.

3. The composition as claimed in claim 1 wherein the step of heating
comprises heating the mixture of compounds, the fuel source, and the
oxidizer to remove water, subsequently allowing the mixture of compounds,
the fuel source, and the oxidizer to gel and heating the gel such that
the gel ignites to form at least one oxide.

4. The composition as claimed in claim 1 wherein the mixture of compounds
comprises at least one compound that is not completely soluble in a
solution.

10. The composition as claimed in claim 1 wherein the composition further
comprises other cementitious particles.

11. A method for making cement compositions, comprising:providing a
mixture of compounds containing the required calcium, silicon, aluminum,
and iron to provide at least one of tricalcium silicate, dicalcium
silicate, tricalcium aluminate, tetracalcium aluminoferrite, other
calcium silicates, aluminates, ferrites, and silicates or combinations
thereof;adding a fuel source and an oxidizer to the mixture of compounds;
andheating the mixture of compounds, the fuel source, and the oxidizer
such that the mixture of compounds, the fuel source, and the oxidizer
ignite to form the at least one tricalcium silicate, dicalcium silicate,
tricalcium aluminate, and tetracalcium aluminoferrite, or combinations
thereof, wherein the at least one tricalcium silicate, dicalcium
silicate, tricalcium aluminate, tetracalcium aluminoferrite, other
calcium silicates, aluminates, ferrites, and silicates, or combinations
thereof each have a particle size of less than about 600 nm.

12. The method as claimed in claim 11 wherein the step of heating
comprises heating the mixture of compounds, the fuel source, and the
oxidizer such that the mixture of compounds, the fuel source, and the
oxidizer foams and subsequently ignites to form the at least one oxide.

13. The method as claimed in claim 11 wherein the step of heating
comprises heating the mixture of compounds, the fuel source, and the
oxidizer to remove water, subsequently allowing the mixture of compounds,
the fuel source, and the oxidizer to gel and heating the gel such that
the gel ignites to form at least one oxide.

14. The method as claimed in claim 11 wherein the mixture of compounds
containing the required calcium, silicon, aluminum, and iron comprises at
least one of limestone, clay, silica fume, blast furnace slag, and fly
ash, or combinations thereof.

15. The method as claimed in claim 11 wherein the step of providing a
mixture of compounds comprises providing a mixture of compounds
containing the required calcium, silicon, aluminum, and iron to provide
two or more of tricalcium silicate, dicalcium silicate, tricalcium
aluminate, tetracalcium aluminoferrite, other calcium silicates,
aluminates, ferrites, and silicates, or combinations thereof.

16. The method as claimed in claim 11 wherein the step of adding a fuel
source comprises adding urea.

17. The method as claimed in claim 11 wherein the step of heating
comprises heating the mixture of compounds, the fuel source, and the
oxidizer to about 300.degree. C.

18. The method as claimed in claim 11 further comprising providing at
least one acid prior to the step of heating.

19. The method as claimed in claim 18 wherein the at least one acid is
selected from nitric acid, citric acid, and acetic acid, or combinations
thereof.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001]This application claims priority to and any other benefit of U.S.
Provisional Application Ser. No. 60/891,663, filed Feb. 26, 2007, the
disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

[0002]Ordinary Portland Cement is one of the basic binder ingredients of
concrete and mortar and is a controlled chemical combination of compounds
made from calcium, silicon, aluminum, and iron oxides, along with small
amounts of other materials. These compounds are typically formed using
naturally occurring materials. Ordinary Portland Cement may have four
primary phases: tricalcium silicate ("C3S") (Ca3SiO5);
dicalcium silicate ("C2S") (Ca2SiO4); tricalcium aluminate
("C3A") (Ca3Al2O6); and tetracalcium aluminoferrite
("C4AF") (Ca4Al2Fe2O10). Other cementitious
materials may also be used as one of the basic binder ingredients of
concrete and mortar.

[0003]The raw materials used to produce cement may be limestone, clay,
shale, sand, or iron ore. The current manufacturing process may consist
of proportioning the raw materials to the correct chemical composition
and grinding them to a fine consistency. The ground material is then fed
to a rotary kiln, which is a large cylindrical continuously rotating
furnace, and heated in the 1500 to 1600° C. range. The raw
materials are calcined, become partially molten, and react to form the
four complex compounds shown above. These compounds exit the kiln as a
hard, sintered agglomerate form called "clinker." The clinker is cooled,
mixed with approximately 5% gypsum, and ground into its final powder
form. Gypsum (calcium sulfate, CaSO4.2H2O) is a necessary
additive that helps regulate the setting time of concrete and in this
respect becomes the fifth major ingredient of cement. Without the
inclusion of gypsum, the hydration rate of the calcium aluminate phase,
C3A, is too fast and would not allow enough time to "work" or
"place" a concrete mixture before setting. An exemplary preparation
process in shown in FIG. 1.

[0004]The chemical composition of cement is what distinguishes one type
from another. Typical ASTM Type I Portland cement comprises approximately
the following percents by weight: 50% C3S, 25% C2S, 10%
C3A, 10% C4AF, and 5% gypsum. However, the industry usually
identifies the cement by the amount of oxides in the raw materials, such
as lime (CaO) and silica (SiO2). Lime and silica make up about 85%
by mass of the final product. When the four primary cement phases are
listed as basic oxides Ordinary Portland Cement approximately comprises
the following percents by weight: 64% CaO, 22% SiO2, 6%
Al2O3, and 3% Fe2O3.

[0005]Concrete is produced by mixing cement with fine aggregate (sand),
coarse aggregate (crushed stone), water, and possibly small amounts of
additives to alter the properties. For example, a concrete mix may
contain the following by weight: about 12% Portland cement, about 34%
sand, about 48% crushed stone, and about 6% water. The setting and rate
of strength development of concrete can be varied by the use of alternate
cement compositions as designated by ASTM. Compositions for the major 5
types of ASTM Portland cement are shown in Table 1. In addition to the
composition shown for each type of Portland cement, the mixture also
contains an additional 5-7% ground gypsum.

[0006]Mortar, on the other hand, is the binder material used to both fill
the gaps and to bond between "blocks" used in construction. These blocks
may be stone, brick, cinder block, manufactured concrete shapes, etc. The
primary ingredient in mortar is the same Portland cement used in
concrete. Mortar is essentially a mixture of sand, Portland cement
(sometimes with and/or without lime), and water. It is applied as a paste
which then sets hard in a similar fashion as concrete. Mortar is
literally the glue that holds the wall system together. It can also be
used to fix masonry when the original mortar has been washed away. Even
though mortar makes up as little as 7% of the total volume of a masonry
wall, it plays a crucial role in the performance of the structure. It not
only bonds the individual units together, but it also seals the building
against moisture and air penetration. While compression strength and
durability are critical properties of concrete, bond strength and
durability are the critical properties of mortar.

[0007]When water is added to cement, each of the compounds undergoes a
hydration reaction that forms the cementatious gel that surrounds and
holds or binds the additional aggregate materials together and to form a
strong solid. Each of the primary phases contributes to the overall
physical and chemical characteristics of the final cementatious product.

[0008]A significant amount of energy is required to manufacture
traditional cement. For example, in the US, plants required an average of
about 5.0 MMBtu/tonne of cement manufactured with the most energy
efficient plant requiring about 3.2 MMBtu/tonne. The average rotary kiln
operation uses about 93% of the total energy, with clinker grinding
requiring approximately 5%. In addition, the rotary kilns may operate at
only 34% energy efficiency. Another downside to the current cement
manufacturing process is the exhaustion of CO2 emissions. For every
tonne of cement produced in a rotary kiln, approximately 1 tonne of
CO2 is released to the atmosphere from the CO2 content of the
starting limestone and in the combustion of fossil fuel that provides the
heat needed for clinker production.

[0009]Thus, there remains a need in the art for more energy efficient
methods of producing cement. Additionally, there remains a need in the
art for cement compositions that can provide concrete exhibiting improved
properties.

SUMMARY

[0010]In accordance with embodiments of the present invention, cement
compositions are provided. The cement compositions comprise at least one
oxide having a particle size of less than about 600 nm. The at least one
oxide is selected from tricalcium silicate, dicalcium silicate,
tricalcium aluminate, and tetracalcium aluminoferrite, other calcium
silicates, aluminates, ferrites, silicates or combinations thereof. The
at least one oxide is made by providing a mixture of compounds containing
the required calcium, silicon, aluminum, and iron for the at least one
oxide, providing a fuel source and an oxidizer to the mixture of
compounds; and heating the mixture of compounds, the fuel source, and the
oxidizer such that the mixture of compounds, the fuel source, and the
oxidizer ignite to form the at least one oxide.

[0011]In accordance with other embodiments of the present invention,
methods for making cement compositions are provided. The methods
comprise: providing a mixture of compounds containing the required
calcium, silicon, aluminum, and iron to provide at least one of
tricalcium silicate, dicalcium silicate, tricalcium aluminate,
tetracalcium aluminoferrite, other calcium silicates, aluminates,
ferrites, and silicates or combinations thereof; adding a fuel source and
an oxidizer to the mixture of compounds; and heating the mixture of
compounds, the fuel source, and the oxidizer such that the mixture of
compounds, the fuel source, and the oxidizer ignite to form the at least
one tricalcium silicate, dicalcium silicate, tricalcium aluminate, and
tetracalcium aluminoferrite, or combinations thereof, wherein the at
least one tricalcium silicate, dicalcium silicate, tricalcium aluminate,
tetracalcium aluminoferrite, other calcium silicates, aluminates,
ferrites, and silicates, or combinations thereof each have a particle
size of less than about 600 nm.

[0012]It will be understood that other embodiments are also described
herein.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0013]The following detailed description of embodiments of the present
invention can be best understood when read in conjunction with the
following drawings, where like structure is indicated with like reference
numerals and in which:

[0014]FIG. 1 is a schematic illustration of one method of preparing
Ordinary Portland Cement;

[0015]FIG. 2 is a schematic illustration of an exemplary method of
preparing cement compositions in accordance with embodiments of the
present invention;

[0016]FIG. 3 is a XRD pattern of a cement composition in accordance with
embodiments of the present invention;

[0017]FIG. 4 is a SEM of a cement composition in accordance with
embodiments of the present invention;

[0018]FIG. 5 is a SEM of Ordinary Portland Cement;

[0019]FIG. 6 is a chart of compressive strength of various cement/sand
mortars in accordance with embodiments of the present invention;

[0020]FIG. 7 is a XRD pattern of a cement composition in accordance with
embodiments of the present invention;

[0021]FIG. 8 is a XRD pattern of a cement composition in accordance with
embodiments of the present invention;

[0022]FIG. 9 is a XRD pattern of a cement composition in accordance with
embodiments of the present invention; and

[0023]FIG. 10 is a DTA curve showing changes occurring during heating in
accordance with embodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0024]The present invention will now be described with occasional
reference to the specific embodiments of the invention. This invention
may, however, be embodied in different forms and should not be construed
as limited to the embodiments set forth herein. Rather, these embodiments
are provided so that this disclosure will be thorough and complete, and
will fully convey the scope of the invention to those skilled in the art.

[0025]Unless otherwise defined, all technical and scientific terms used
herein have the same meaning as commonly understood by one of ordinary
skill in the art to which this invention belongs. The terminology used in
the description of the invention herein is for describing particular
embodiments only and is not intended to be limiting of the invention. As
used in the description of the invention and the appended claims, the
singular forms "a," "an," and "the" are intended to include the plural
forms as well, unless the context clearly indicates otherwise. All
publications, patent applications, patents, and other references
mentioned herein are incorporated by reference in their entirety.

[0026]Unless otherwise indicated, all numbers expressing quantities of
ingredients, properties such as molecular weight, reaction conditions,
and so forth as used in the specification and claims are to be understood
as being modified in all instances by the term "about." Accordingly,
unless otherwise indicated, the numerical properties set forth in the
following specification and claims are approximations that may vary
depending on the desired properties sought to be obtained in embodiments
of the present invention. Notwithstanding that the numerical ranges and
parameters setting forth the broad scope of the invention are
approximations, the numerical values set forth in the specific examples
are reported as precisely as possible. Any numerical values, however,
inherently contain certain errors necessarily resulting from error found
in their respective measurements.

[0027]In accordance with embodiments of the present invention, cement
compositions and methods of making cement are provided. The cement
compositions include one or more oxides having an average particle size
of less than about 600 nm.

[0028]In some embodiments, cement compositions are provided. The cement
compositions comprise at least one oxide having an average particle size
of less than about 600 nm. The at least one oxide is selected from
tricalcium silicate, dicalcium silicate, tricalcium aluminate,
tetracalcium aluminoferrite, other calcium silicates, aluminates,
ferrites, and silicon oxide or combinations thereof.

[0029]The at least one oxide may be made in any suitable manner. In some
embodiments, the at least one oxide is made by providing a mixture of
compounds containing the required calcium, silicon, aluminum, and iron
for the at least one oxide, providing a fuel source and an oxidizer to
the mixture of compounds, and heating the mixture of compounds, the fuel
source and the oxidizer such that the mixture of compounds and the fuel
source and oxidizer all ignite to form the at least one oxide. In some
examples, the mixture of compounds, the fuel source, and the oxidizer are
heated such that the mixture of compounds, the fuel source, and the
oxidizer foams and subsequently ignites. In other examples, the mixture
of compounds and/or the fuel source and/or the oxidizer are heated to
remove water and subsequently allowed to gel before the step of heating
to ignition.

[0030]It will be understood that the mixture of compounds may be provided
in any suitable manner. For example, the calcium, silicon, aluminum, and
iron containing compounds may be provided in any suitable ratio to
provide a desired final product. For example, the mixture of compounds
can be chosen to provide one of the oxides, more than one of the oxides,
or all of the oxides. In some examples, the oxides may be made separately
and subsequently combined to form the cement compositions. In other
examples, the oxides may be made simultaneously to form the cement
compositions.

[0031]In further examples, the mixture of compounds may be in any suitable
form. For example, reagent grade compounds including, but not limited to,
calcium carbonate, a silica source, aluminum nitrate, and iron nitrate
may be used in the mixture of compounds. Additionally, the compounds may
be provided in any suitable form. For example, the compounds may comprise
hydrates, carbonates, and/or nitrates. In other examples, non-reagent
grade materials or naturally occurring materials including, but not
limited to, limestone, clay, silica fume, and fly ash blast furnace slag,
and iron oxide from iron/steel processing may be used. In yet further
examples, waste oxides, such as calcium hydroxide and/or calcium oxide
may be used from waste sources.

[0032]It will be understood that the amounts of each of the compounds in
the mixture may be chosen based on the desired final cement composition.
The cement industry frequently reports the composition of cement as a
percentage of the raw material oxides as CaO, SiO2, Al2O3,
and Fe2O3 instead of as the final compounds formed. For
example, for a product containing multiple at least one oxides the major
product percentages may be about 45% to 67% CaO, 18% to 41% SiO2, 0%
to 14% Al2O3, and 0% to 5% Fe2O3 of one or
combinations of these. In addition, the single compounds of the major
phases may be produced and as such have their product composition fixed
by the chemical formula of the compound. For example, C3S comprises
74% CaO and 26% SiO2, C2S comprises 65% CaO and 35% SiO2,
C3A comprises 62% CaO and 38% Al2O3, and C4AF
comprises 46% CaO, 21% Al2O3, and 33% Fe2O3.

[0033]In some examples, at least one of the compounds in the mixture may
be a compound that is not completely soluble in a solution containing the
mixture of compounds. For example, one of the compounds may be partially
or completely insoluble in the solution. In another example, more than
one of the compounds may be partially or completely insoluble in the
solution. In yet another example, all of the compounds may be partially
or completely insoluble in the solution. In other examples, the compounds
in the mixture may be provided as homogenous or non-homogeneous mixtures.
For example, the mixture of compounds may be provided in an aqueous or
non-aqueous solution as well as homogeneous and non-homogeneous mixtures.
As discussed above, at least one of the compounds may not be partially or
completely soluble in the solution. However, the presence of such
compounds does not prevent the formation of the desire oxide. For
example, silicon may be provided in the form of silica fume that may not
be soluble in a solution containing the mixture of compounds. In this
example, the compounds containing the required calcium, aluminum, and/or
iron may be mixed in solution, the fuel source added, and the silica fume
subsequently added to the mixture prior to heating. It will be understood
that the mixture of compounds and the fuel source may be provided in any
suitable manner and in any suitable order. It will be further understood
that the solution may be any suitable solution. In some examples, soluble
compounds may be dissolved in various acidic solutions including but not
limited to nitric acid, acetic acid, citric acid, other acids or
combinations thereof.

[0034]Any suitable fuel source may be used. For purposes of defining and
describing the present invention, the term "fuel source" shall be
understood as referring to any compound that may be used to provide fuel
for a combustion reaction that occurs upon heating the mixture of
compounds. For example, the fuel source may comprise urea, glycine,
carbohydrates, petroleum products, and/or hydrogen. In some examples, the
fuel source is chosen to assist in gelling of the mixture after the
mixture is heated to remove water, when such a heating step is performed.
In other examples, the fuel source is not chosen to assist in gelling of
the mixture after the mixture is heated to remove water, when such a
heating step is performed. Any suitable amount of the fuel source may be
used, and one having skill in the art would be able to choose the fuel
source and amount to provide a desired combustion reaction. In some
examples, urea is used as the fuel source and the urea may be provided in
an amount of about 2.5:1 by weight of urea to product ratio to about
3.6:1 by weight of urea to product ratio.

[0035]The fuel source may also include additional additives. For example,
the additive fuel source may include additives that can aid in foaming or
combustion. Examples of suitable additives include, but are not limited
to, acetic acid and citric acid, or combinations thereof.

[0036]Any suitable oxidizer may be used. For purposes of defining and
describing the present invention, the term "oxidizer" shall be understood
as referring to any suitable source of oxygen for the combustions
reaction. Examples of suitable oxidizers include, but are not limited to,
nitric acid, oxygen, air, calcium nitrate, ammonium nitrate, and any
other suitable oxygen containing compound.

[0037]The step of heating the mixture of compounds, the oxidizer, and the
fuel source may be performed in any suitable manner and at any suitable
temperature or temperatures. For example, the mixture of compounds,
oxidizer, and/or fuel source may be initially heated to remove water and
then heated to a temperature sufficient to ignite the mixture such that a
combustion reaction occurs. In some examples, the mixture may be allowed
to gel after the initial heating step to remove water and before the step
of heating until the mixture is heated to ignition. In other examples,
the mixture may be heated until the mixture foams and to a temperature
sufficient to ignite the mixture such that a combustion reaction occurs.
One such exemplary schematic approach is illustrated in FIG. 2. The
foaming may keep non-dissolved materials uniformly suspended and mixed.
It will be understood that the foaming does not necessarily have to
occur.

[0038]Once the mixture is heated to a temperature sufficient to initiate
the combustion reaction, the temperature rises rapidly and reactions
occur to form the at least one oxide. It will be understood that the
amounts of each oxide can be controlled depending on the ratio of the
mixture of compounds and the temperature achieved during combustion. Any
suitable temperature may be used to ignite the mixture. For example, the
ignition temperature may be less than about 300° C., about
300° C., about 400° C., about 500° C., about
600° C., or more than about 600° C. The mixture may be
heated to the ignition temperature in any suitable manner. For example,
the mixture may be placed in or on a heat source that is slowly raised to
the ignition temperature or that is quickly raised to the ignition
temperature. In another example, the mixture may be placed in or on a
heat source that is already at or above the ignition temperature. It will
be understood that the particular temperature for igniting the mixture
will vary based on the particular mixture of compounds, amounts of the
compounds, the particular fuel source, the amount of the particular fuel
source, the particular oxidizer, the amount of particular oxidizer and
the presence of any additional additives. It will be further understood
that the particular manner of heating is merely a matter of convenience
and any suitable method of heating may be used.

[0039]Once combustion occurs, the at least one oxide or mixture of oxides
comprises nanoscale oxide particles. The nanoscale oxide particles may be
of any suitable size. For example, the oxide particles may have an
average particle size of less than about 600 nm, less than about 500 nm,
less than about 400 nm, less than about 300 nm, less than about 200 nm,
less than about 100 nm, and less than about 20 nm, or combinations
thereof. It will be understood that the oxide particles may have any
suitable range of size distributions.

[0040]The particles may be loosely aggregated, and the particles may be
further processed in any suitable manner. For example, the particles may
be ground or screened. In some examples, the particles may be ground or
screened so that they pass through a sieve having a mesh size of from
about 40 to about 400, or from about 100 to about 325. In another
example, gypsum may be added to the at least one oxide in any suitable
amount.

[0041]In yet further examples, the at least one oxide may be used to
replace Ordinary Portland Cement particles in any suitable manner and in
any suitable amount, including entirely replacing Ordinary Portland
Cement in such applications where it is used. Examples of such
replacement amounts, include but are not limited to, from about 2% by
weight of a mixture containing mainly Ordinary Portland Cement and the at
least one oxide to entirely replacing Ordinary Portland Cement such that
the at least one oxide comprises 100% of the cement. In some examples,
less than about 2% by weight of the at least one oxide may be used as a
replacement for Ordinary Portland Cement. For purposes of describing and
defining the present invention, the term "Ordinary Portland Cement" shall
be understood as referring to a cement having particles of at least one
of tricalcium silicate ("C3S"), dicalcium silicates ("C2S"),
tricalcium aluminate ("C3A"), and tetracalcium aluminoferrite
("C4AF"), or combinations thereof, and the particles having an
average particle size of greater than about 5 μm. In other examples,
the at least one oxide may be added to any suitable concrete composition
in any suitable amount.

[0042]In yet other examples, the at least one oxide may be used to replace
other cementitious particles in any suitable manner and in any suitable
amount, including entirely replacing other cementitious particles in such
applications where it is used. Examples of such replacement amounts,
include but are not limited to, from about 2% by weight of a mixture
containing mainly other cementitious particles and the at least one oxide
to entirely replace other cementitious particles such that the at least
one oxide comprises 100% of the cement. In some examples, less than about
2% by weight of the at least one oxide may be used as a replacement for
other cementitious particles. For purposes particles materials" shall be
understood as referring to a cement having aggregate particles that are
not classified as Ordinary Portland Cement and the particles having an
average particle size of greater than about 5 μm.

[0043]The cement compositions of the present invention may exhibit
increased surface areas in comparison to Ordinary Portland Cement. In
some examples, surface areas from about 2 to about 10 times greater than
Ordinary Portland Cement are achieved. In addition, the cement
compositions of the present invention may exhibit increased strength in
comparison to Ordinary Portland Cement or when used as a replacement to
Ordinary Portland Cement. In cases where the at least one oxide cement
compositions are used as a replacement for Ordinary Portland Cement in
mortar or concrete formulations, it will be understood that the cement
compositions may be used in any suitable amounts in the range of about 2
to about 100% by weight.

[0044]The present invention will be better understood by reference to the
following examples which are offered by way of illustration not
limitation.

EXAMPLES

Example 1

[0045]Calcium carbonate (365 g) was dissolved in nitric acid (677 g). To
this solution, aluminum nitrate (123 g), iron nitrate (44 g), and urea
(1080 g) were added and heated until dissolved. Then silica fume (134 g)
was added to the solution and finally 17 grams each of citric acid and
acetic acid were added. The solution was heated until all the water was
evaporated and the resulting slurry was transferred into an oven heated
to 500° C. The solution foamed and combusted resulting in a
loosely aggregated product with a yield of 320 grams. The product was
ground and analyzed by XRD to identify the composition. The oxide product
comprised CS, C2S, C3S, CaO, C4AF, and C3A as shown
in FIG. 3. A SEM was also completed to determine the particle size. As
shown in FIG. 4, the primary particle sizes of the nano-cement were
approximately 200 to 500 nm. FIG. 5 illustrates an SEM of Ordinary
Portland Cement, and it can be seen that the average particle size is
greater than about 5 μm.

Example 2

[0046]The oxide composition from example 1 was mixed with 5% gypsum and
ball milled to break up the aggregates so that it passed through a 200
mesh sieve. It was then mixed with sand, silica fume, water and Ordinary
Portland Cement in various amounts to determine the effect of compressive
strength for the different compositions per ASTM C109.

[0047]To document and compare the setting time of the at least one oxide
containing compositions produced to those of standard or Ordinary
Portland Cement (OPC), the procedures outlined in ASTM C-191, "Test
Method for Time of Setting of Hydraulic Cement by Vicat Needle," were
followed. This procedure consisted of mixing 200 grams of cement or
blended cement, with 95 grams of water, placing the paste in the
appropriate support or container and recording the elapsed time from
addition of water to the time when the Vicat needle does not sink visibly
into the paste. For each experimental test, a standard sample of OPC was
prepared for a direct comparison.

[0048]In all cases, 73.3 parts of sand were mixed with 26.7 parts of total
cementatious materials while maintaining the water to cement ratio at
0.485. Mortar cylinders were made and stored wet. The percent of relative
compressive strength for each composition was measured as a function of
time. Sample 4 consistently demonstrated higher compressive strength, and
the rate strength development did not slow down like the other samples
during the entire 28 day testing. The compositions and strength results
are given in Table 2 and a chart is shown in FIG. 6.

[0049]In this example, it is shown that the single compound C3A may
be produced. Calcium carbonate (202 g) was dissolved in nitric acid (372
g). To this solution, aluminum nitrate (506 g) and urea (546 g) were
added and heated until dissolved. The solution was heated until all the
water was evaporated and then 9.7 grams each of citric and acetic acid
were added and the resulting slurry was transferred into an oven heated
to 500° C. The solution foamed and combusted resulting in a
loosely aggregated product with a yield of 162 grams. The product was
ground and analyzed by XRD. The product comprised primarily C3A as
shown in FIG. 7.

Example 4

[0050]In this example, it is shown that the single compound C4AF may
be produced. Calcium carbonate (206 g) was dissolved in nitric acid (362
g). To this solution, aluminum nitrate (386 g), iron nitrate (416 g), and
urea (643 g) were added and heated until dissolved. The solution was
heated until all the water was evaporated and then 9.5 grams each of
citric and acetic acid were added and the resulting slurry was
transferred into an oven heated to 500° C. The solution foamed and
combusted resulting in a loosely aggregated product with a yield of 225
grams. The product was ground and analyzed by XRD. The product comprised
primarily C4AF as shown in FIG. 8

Example 5

[0051]In this example, it is shown that mined materials such as clay may
be used to produce a desired product which is similar to the product in
example 1. In this example, the clay provides the source for SiO2,
Al2O3, and Fe2O3. Calcium carbonate (100 g) was
dissolved in nitric acid (186 g). To this solution, clay (60 g) and urea
(400 g) were added and heated to remove the water. Next, 5.4 grams each
of acetic acid and citric acid were added. The resulting slurry was
transferred into an oven heated to 500° C. The solution foamed and
combusted resulting in a loosely aggregated product with a yield of 100
grams. The product was ground and analyzed by XRD and is shown in FIG. 9.
The product was determined to have a similar composition to that from
example 1.

Example 6

[0052]Experiments were performed using both reagent grade raw materials
and mined raw materials. For reagent grade experiments, calcium carbonate
(CaCO3), nitric acid (HNO3), aluminum nitrate
[Al(NO3)3.9H2O], iron nitrate
[Fe(NO3)3.9H2O], silica fume (SiO2), and urea
[CO(NH2)2] were used to synthesize C2S, C3S,
C3A, C4AF individual phases, as well as samples containing all
four phases. For the mined raw material experiments, limestone, clay,
nitric acid, and urea were used to synthesize cement products similar to
the reagent grade products.

[0053]In an exemplary experiment, reagent grade CaCO3 powder was
dissolved in a beaker containing dilute HNO3 and stirred until a
clear solution was obtained. Next, Al(NO3)3.9H2O and
Fe(NO3)3.9H2O were added as necessary and dissolved. Urea
was then added to the reaction mixture and the solution was heated. Once
all the urea was dissolved, silica fume (SiO2) was added. In
addition acetic acid and citric acid were sometimes added depending on
the experimental formulation. The solution was mixed and stirred on hot
plate to reduce the volume (free water). Once the solution was heated to
the expected zero percent water level, the slurry was transferred to a
stainless steel container where it was allowed to cool and gel. The gel
was then placed in a kiln and heated to combustion.

[0054]In other examples, mined raw materials such as limestone were first
dissolved in nitric acid, followed by the addition of other soluble
ingredients, then the urea, followed by the remaining insoluble powders
(silica sources, clays, etc.), heating to remove all water, gelling in
stainless reactor pan, followed by heating to combustion was performed.

[0055]The experiments also included measuring the temperature profile
during heating to determine temperature of dehydration, foaming, auto
ignition temperature, and the extent of the exothermic reaction;
performing a XRD analysis to determine the types of cement phases formed;
measuring surface area and particle size on select samples; DTA on select
compositions; checking the ability of the ground paste to form a
cementatious, hydraulic bond; and using the ground product to make small
cement-mortar sand samples for measuring the rate of compression strength
development and cement setting time.

[0056]Compositions and some results are shown in the following tables.

[0057]In addition, FIG. 10 shows an exemplary DTA curve depicting the
different stages of the combustion reaction. Initially, any excess water
is driven off up to the melting point of urea which is 132° C.
After 132° C., the sample starts foaming, then thickens until
270-300° C., at which time combustion is initiated.

[0058]The present invention should not be considered limited to the
specific examples described above, but rather should be understood to
cover all aspects of the invention. Various modifications, equivalent
processes, as well as numerous structures and devices to which the
present invention may be applicable will be readily apparent to those of
skill in the art.